avrapps-1544: getting started with events on the tinyavr 1...

Getting Started with Eventson the tinyAVR 1-series

Getting Started with Events on the tinyAVRreg 1-series

Prerequisites

bull Hardware Prerequisitesndash ATtiny817 Xplained Pro evaluation kitndash Micro-USB cable (Type-AMicro-B)ndash A breadboardndash A compatible potentiometerndash Three compatible male-to-female wiresndash Internet connection

bull Software Prerequisitesndash Atmel Studio 70ndash Web browser A list of supported browsers can be found here httpstartatmelcomstatic

helpindexhtmlGUID-51435BA6-0D59-4458-A413-08A066F6F7CAbull Estimated Completion Time 120 minutes

Introduction

This hands-on training will demonstrate how to develop AVRreg applications in Atmel Studio and AtmelSTART along with the rich user interface and other great development tools that they provide

Atmel START helps to get started with Microchip microcontroller development It allows to select MCUconfigure software components drivers middleware and example projects to the embedded applicationin a usable and optimized manner Once the configuration is complete the project can be generated inAtmel Studio or another third-party development tool An IDE is used to develop the code required toextend the functionality of the project into the final product as well as compile program and debug thedownloaded code

With Atmel START

bull Get help selecting the MCU based on both software and hardware requirementsbull Find and develop examplesbull Configure drivers middleware and example projectsbull Get help with setting up a valid PINMUX layoutbull Configure system clock settings

The ATtiny817 Xplained Pro evaluation kit is a hardware platform for evaluating the AVR ATtiny817microcontroller A fully integrated embedded debugger is included on the kit which provides seamlessintegration with Atmel Studio Easy access to the features of the ATtiny817 is enabled by the kitfacilitating easy integration of the device in a customer design

This training demonstrates how to configure the application in Atmel START Reconfigure the AtmelSTART project and continue the implementation in Atmel Studio 7

copy 2017 Microchip Technology Inc Training Manuals DS00002533A-page 1

The peripherals used to create applications are GPIO RTC ADC CPUINT USART and Event System

Figure 1 ATtiny817 Xplained Pro

The following topics are covered

bull Driver configuration in Atmel STARTbull PINMUX driver configurationbull LED toggling triggered by RTC overflow interruptbull USART configuration with string print to USART serial-port terminalbull RTC overflow interrupt triggers an ADC conversion and then ADC result-ready interrupt triggers ADC

data print to USART terminalbull RTC overflow interrupt triggers an ADC conversion and then an ADC result triggers ADC data print to

USART terminal if it is outside a defined windowbull RTC overflow event triggers an ADC conversion then if an ADC result is outside a defined window

waking up CPU with an IRQbull How to use Data Visualizer in Atmel Studio to view the USART print to the embedded terminal and

graph

Getting Started with Events on the tinyAVR 1-series


Table of Contents

Prerequisites1

Introduction1

1 Icon Key Identifiers 5

2 Assignment 1 RTC Overflow Interrupt Triggers LED Toggling 621 Atmel | START Project Creation 622 Atmel | START Project Overview In Atmel Studio 1423 Code Development 1624 Debug the Application 16

3 Assignment 2 RTC Interrupt Triggers String Sent to USART Terminal2031 USART Configuration in Atmel | START 2032 Expand the USART Functionality2433 USART Output to Data Visualizer Terminal2634 RTC Interrupt Triggers USART Transmission 27

4 Assignment 3 ADC ISRRDY Interrupt Triggers ADC Data Output to USARTTerminal 3241 Add ADC Driver In Atmel | START 3242 Configure ADC in Atmel | START3343 Add ADC Functionality to Application Code3644 Connect Potentiometer to ADC3845 Observe ADC Functionality39

5 Assignment 4 ADC WCMP Interrupt Triggers ADC Data Print to Data Visualizer4151 ADC Re-Configuration in Atmel START 4152 Update Application in Atmel Studio and Output ADC Data to Data Visualizer Graph43

6 Assignment 5 RTC Interrupt Replaced by Event System4661 Event System Configuration in Atmel START 4662 Event System Driver Code Development49

7 Conclusion51

8 Revision History52

The Microchip Web Site 53

Customer Change Notification Service53

Customer Support 53

Microchip Devices Code Protection Feature 53

Legal Notice54


Trademarks 54

Quality Management System Certified by DNV55

Worldwide Sales and Service56



1 Icon Key IdentifiersThe following icons are used in this document to identify different assignment sections and to reducecomplexity

Info Delivers contextual information about a specific topic

Tip Highlights useful tips and techniques

To do Highlights objectives to be completed

Result Highlights the expected result of an assignment step

Warning Indicates important information

Execute Highlights actions to be executed out of the target when necessary



2 Assignment 1 RTC Overflow Interrupt Triggers LED TogglingIn this assignment an application that triggers LED toggling from the RTC overflow interrupt will bedeveloped

Atmel | START will be used to configure the RTC clock and PINMUX settings Based on this an AtmelStudio 7 project will be generated

Code will be developed in Atmel Studio 7 using PINMUX and RTC driver functions generated by Atmel |START

Info On the ATtiny817 Xplained Pro board LED0 is connected to pin PB4

Peripherals used

bull RTCbull GPIO (PB4)

Clock details

bull 3333 MHz main clockbull 1 kHz RTC clock

21 Atmel | START Project CreationConfigure PINMUX driver RTC driver and CLOCK in Atmel | START and create the project

To do Create a new Atmel | START Project

1 Open Atmel Studio2 Select File rarr New rarr Atmel Start Project3 The CREATE NEW PROJECT window appears within Atmel Studio 7 In the Filter on device

text box enter 817X then select ATtiny817 Xplained Pro from the list and verify thatATtiny817Xplained Pro is highlighted then click CREATE NEW PROJECT as shown below



Figure 2-1 CREATE NEW PROJECT

Info Now the MY SOFTWARE COMPONENTS window appears

4 In the MY SOFTWARE COMPONENTS window rename the project as shown below with 1-2 redmarkings First click MY PROJECT and then select Rename ComponentFigure 2-2 Rename Component

Info Now RENAME COMPONENT window will be displayed

5 In the RENAME COMPONENT window specify the new project name asATtiny817_getting_start_events and click Rename



6 Open PINMUX configuration by clicking on in the navigation tab on the left side of thewindow

Info The PINMUX configurator displays an illustration of the device package selected Itshows which pins are currently used by different peripherals GPIO pins can beconfigured here

Info Here PB4 is configured as LED0 which is available on the ATtiny817 Xplained ProConfiguration is shown in 1-4 red markings below

Figure 2-3 PINMUX Configuration LED0

7 Execute the numbered configuration steps 1-4 from the figure as described belowndash Click PB4 in the PINMUX listndash Enter User label as LED0ndash Select Pin mode Digital outputndash Make sure Initial level is set to Low

Info Technical documents related to the ATtiny817 Xplained Pro can be downloadedfrom the ATtiny817 Xplained Pro rarr Technical Documentation page within Atmel StudioThe ATtiny817 Xplained Pro page is displayed when the ATtiny817 Xplained Pro board isconnected to the PC

8 Add the RTC component



Click in the navigation tab on the left side of the window Then click

Info The ADD SOFTWARE COMPONENTS window will appear

Figure 2-4 Add RTC Component

9 RTC ConfigurationExpand Drivers in the ADD SOFTWARE COMPONENTS window as shown above scroll downto locate RTC and click to select it Then click the Add component(s) button The RTC_0module will now be added to the project as shown below

Info In the figure below red markings 1-2 refer to what has been completed aboveSteps 3-7 describes the configuration of the RTC



Figure 2-5 RTC Configuration

10 Execute the numbered configuration steps 3 through 7 from the figure above asndash Click RTC_0 to open the RTC driver configuration pagendash Tick the RTCEN checkbox to configure the RTC to be enabled in the RTC initialization

routine that will be generated by Atmel | STARTndash Click the PRESCALER dropdown menu and select 32 to configure the RTC clock

prescaler to 32

Info This will configure the RTC count frequency to 1 kHz as the default RTCclock source is the 32 kHz Internal Ultra Low Power Oscillator



ndash Continue by entering decimal number 500 equivalent to the hexadecimal value 0x1f4 in thePER text box to define the RTC period

ndash Tick the OVF checkbox to enable the RTC overflow interrupt

Info The RTC overflow interrupt is configured to trigger approximately twice per secondas the period is set to 500 with a RTC clock frequency of 1 kHz

11 Enable CPUINT Global Interrupt

Info The three steps involved in configuring the CPUINT module are described belowand illustrated in Figure 2-6

ndash Make sure the Show system drivers slider in the top right corner of the DASHBOARD-viewis switched ON

ndash Click CPUINIT to open the CPUINT configuration viewndash Tick the CPU_SREG Global Interrupt Enable checkbox such that the initialization routine

generated by Atmel | START will enable global interrupts



Figure 2-6 CPUINT Configuration

Info The RTC and CPUINIT are now configured The RTC will now be able to trigger itsoverflow interrupt

12 Clock configuration Open the clock configuration view by clicking on in the navigation tabon the left side of the window



Info The CLOCK CONFIGURATOR view will now be displayed It contains oscillatorsand clock sources of different types Required clock sources can be selected andconfigured The corresponding output frequency is then calculated and presented Thesettings dialog for each element in the clock configuration view can be opened by clickingthe associated cog-wheel

bull The Oscillators section displays the oscillators available for the selected devicebull The Source section is used to configure clock frequency by selecting input signal

and prescaling factor

13 Open the Clock Settings- dialog for Main Clock by clicking its corresponding cog-wheel to viewthe default clock settings as shown below

Info CLOCK SETTINGS window will be displayed

Figure 2-7 MAIN CLOCK CONFIGURATION

Info For this application the default clock settings are kept as is Here the Main Clocksource is the 20 MHz Internal Oscillator with prescaler division set to 6 The resulting CPU

clock frequency is 333 MHz Clicking the question mark next to each configuration willprovide the data sheet description of the individual bit setting The RTC clock wasconfigured to 1 kHz earlier and this is also shown in the figure

14 Click Close to close the CLOCK SETTING window

15 Now click the GENERATE PROJECT button 16 Select the desired path where the project should be stored as shown below and then click OK



Figure 2-8 Project Importer Window

Result The Atmel | START project has been created in Atmel Studio

22 Atmel | START Project Overview In Atmel StudioThe Atmel | START project generates peripheral driver functions and files as well as a main() functionthat initializes all drivers

About folders and files generated by Atmel | START

bull Header files and source files for the peripheral drivers generated by START are located in thefolders src and include

bull The atmel_start_pinsh file in the include folder contains useful PINMUX driver functionsbull The utils folder contain files that define some functions that can be commonly used by the drivers

and the application itselfbull The atmel_startc file contains the atmel_start_init() function which initializes the MCU

drivers and middleware defined for the projectbull The driver_isrc file contains generated ISRs if interrupts have been enabled in Atmel | START

To do Get an overview of the Atmel | START project



Figure 2-9 Project Overview

1 The Solution Explorer sub-window for the generated ATtiny817_getting_started_events Studioproject should be present as shown in the figure above If not click on the Solution Explorer sub-window as indicated in the figure to unhide it It can also be opened by clicking View followed bySolution Explorer Double-click the mainc file in the Solution Explorer sub-window to open it

2 Right-click on the atmel_start_init() function and then click Goto Implementation Repeat theprocedure for the system_init() function which is called by atmel_start_init() andobserve that system_init() calls the initialization functions for the generated peripheral drivers

Info The mcu_init() function enables the internal pull-up resistor on all pins to reducepower consumption All driver initialization functions are called from the system_init()function in addition to configuring the port pin associated with LED0 to output mode witha defined initial level

3 Go to implementation of CLKCTRL_init() and observe that the default clock settings arecommented out

Info If the non-default clock settings are selected in START it will be reflected inCLKCTRL_init()

4 Open the atmel_start_pinsh file in the Solution Explorer sub-window and then click on the downarrow as shown in the figure below to open the list of functions defined in this file Observe thatmany useful GPIO functions have been generatedFigure 2-10 atmel_start_pinsh Functions



Result The Atmel | START project overview is completed

23 Code DevelopmentHere the RTC overflow interrupt will be set up to trigger LED0 toggling on the ATtiny817 Xplained Prodevelopment kit

To do Write code to toggle LED0 in the RTC interrupt handler

1 Open the driver_isrc file in the ATtiny817_getting_started_events project

To do Edit the driver_isrc file

2 Insert the code LED0_toggle_level() in the ISR(RTC_CNT_vect) interrupt handler asshown below This will as the function name reveals toggle the level on the pin connected to LED0each time the RTC overflow interrupt is executedISR(RTC_CNT_vect) Insert your RTC Overflow interrupt handling code LED0_toggle_level() Overflow interrupt flag has to be cleared manually RTCINTFLAGS = RTC_OVF_bm

Info Since the RTC clock runs at 1 kHz and the RTC period is set to 500 the RTCoverflow interrupt will be executed two times per second LED0 will consequently toggletwo times per second

3 The mainc file is kept as is Click Build rarr Build Solution in the top toolbar or press F7 in AtmelStudio to build the solutionNote The build should finish successfully with no errors

24 Debug the Application

To do Debug the application where the RTC overflow interrupt triggers LED0 toggling



1 Power the ATtiny817 Xplained Pro kit by connecting a Micro-USB cable to the computer2 In Studio click Debug rarr Start Debugging and Break to program the kit and start debugging as

shown below This can also be done by pressing Alt+F5Figure 2-11 Start Debugging and Break

Info If the embedded debugger firmware version on is lower than the one in the AtmelStudio installation a firmware upgrade dialog will be opened

Figure 2-12 Firmware Upgrade

Select Upgrade and when the progress bar is complete select Close Now start debugging byclicking Debug rarr Start Debugging and Break or by pressing Alt+F5



Result The kit is programmed with the application and a debugging session is initiatedstarting with the code in mainc

3 Click in the margin to the left of the RTCINTFLAGS = RTC_OVF_bm to place a breakpoint in thecode in driver_isrc as shown above This breakpoint is set after the LED0_toggle_level()function call is executed

4 Run the application until the breakpoint is hit by clicking Debug rarr Continue pressing F5 or by

clicking the play button

Tip The play button is located in the top toolbar in Atmel Studio and in the Debugmenu

5 To check the status of all the PORTB pins open the IO View window by selecting Debug rarrWindows rarr IO and click on the IO Ports (PORTB) register group as shown in Figure 2-13

Info In the IO View the status and register values of all peripherals can be inspectedPin status is indicated for PB0 to PB7 from right to left under the Bits column in the OUTregister As shown in the image below the level of pin PB4 (LED0) is HIGH since a filledsquare corresponds to bit status 1 An empty square indicates that the bit status is 0LOW



Figure 2-13 IO View

6 Click on to continue the execution and observe that the value of the OUT register in thePORTB register alternates between 0x00 and 0x10 each time the breakpoint is hit This indicatesthat pin PB4 is being set and reset alternatively and LED0 is toggling correspondingly

7 Remove the breakpoint by clicking the shown in Figure 2-11 and run the code again by

pressing F5 or clicking Now LED0 should continuously toggle two times per second8 End the debugging session by clicking Debug rarr Stop Debugging pressing Ctrl+Shift+F5 or by

clicking

Result An application that toggles LED0 on the RTC overflow interrupt has beensuccessfully programmed on the ATtiny817 Xplained Pro evaluation kit



3 Assignment 2 RTC Interrupt Triggers String Sent to USART TerminalIn this assignment it will be demonstrated how to configure the USART module and use it to send astring as well as how to display the string Hello World in the terminal embedded in the Atmel StudioData Visualizer An application will be developed so that the RTC overflow interrupt when set will triggerreading of the string from the USART and output it in the terminal

First Atmel | START will be used from within Studio to reconfigure the project from Assignment 1 InSTART the USART component will be added to the project and then configured The basic USARTdrivers will be automatically generated from START for the project in Studio An extended USARTfunction code is required to be added manually in Studio

Peripherals used

bull USARTbull RTC (from previous assignment)bull GPIO (PB4 from previous assignment)

Clock details

bull 3333 MHz main clockbull 1 kHz RTC clock (from previous assignment)

31 USART Configuration in Atmel | START

To do Add the USART driver and configure the module in Atmel | START by reconfiguring theproject from within Atmel Studio

Info The ATtiny817 Xplained Pro is equipped with the Atmel Embedded Debugger (EDBG)which identifies itself as a composite USB device with a Virtual COM Port interface whenconnected to a computer The Virtual COM Port is connected to the UART on the ATtiny817 viathe EDBG and provides an easy way to communicate with the target application throughterminal software It offers variable baud rate parity and stop bit settings Note that the settingson the ATtiny817 must match the settings given in the terminal software

Tip The USART TX line on the device on ATtiny817 Xplained Pro connected to the EDBGVirtual COM Port is available on pin PB2

1 Open the ATtiny817_getting_started_events project from assignment 12 Right-click on ATtiny817_getting_started_events in the Solution Explorer window the sub window

pops up In the sub-window select Re-Configure Atmel START Project as shown in the figurebelow



Figure 3-1 Re-Configure Atmel | START Project

Info Atmel | START will be opened in the default web browser in Studio

To do Add in the USART component

3 Open the ADD SOFTWARE COMPONENTS window by clicking 4 Expand the Drivers category and scroll down to locate the USART driver Click it to select it and

then click Add Component(s) as shown below



Figure 3-2 Add Software Components

Result The USART driver will now be added to the project

To do Configure the USART baud rate to 9600 and enable the transmitter

5 Click the newly added USART_0 box to open the driver configuration viewFigure 3-3 USART Configuration



6 Perform the configuration steps in red markings as illustrated in the figure abovendash Click the TXD dropdown menu under SIGNALSndash Select PB2 as TXD pinndash Tick the TXEN checkbox to let the USART transmitter to be enabled in the USART

initialization routine which will be generated by STARTndash Observe that the default baud rate is 9600 and leave it as is

Result The USART driver configuration is completed

7 Click the GENERATE PROJECT button at the bottom of the window to regenerate the project inAtmel StudioFigure 3-4 Project Code Regenerated

Result The Project Summary window will appear as shown in the figure above

Info The Project Summary gives an overview of the differences between the originaland the reconfigured Studio project Clicking View Diff as shown in figure above willopen the external WinMerge tool which shows the changes to that file This externalWinMerge tool is not installed within Studio by default Here is the info on how to install it



ndash Download the tool from httpdownloadssourceforgenetwinmergeWinMerge-2140-Setupexe

ndash Install the tool at the default path (ie CProgram Files (x86)WinMerge) or a user-definedpath

ndash In Atmel Studio go to the Tools Options rarr Atmel Start rarr File Compare menu In ldquoPath of theapplication used for comparing filesrdquo enter CProgram Files (x86)WinMergeWinMergeUexe In ldquoCommand line arguments to be used for file comparisonrdquo enteroriginal mine s u

ndash Click OK and the View Diff as shown in Figure 3-4 should work now8 Since we do not want to overwrite the driverisrc file there is no need to inspect this file Leave the

checkbox unticked and click OK as illustrated in the figure above to regenerate the project for AtmelStudio

Result The project will be regenerated in Studio including reconfiguration updatesperformed in Atmel | START

32 Expand the USART Functionality

To do In Atmel Studio add code to the USART peripheral to send the string Hello Worldand output it to terminal

1 In Studio Solution Explorer window locate the usartc file under the src directory as shown in Figure 3-5 and double-click to open it

2 Expand the function list by clicking the arrow as shown in the red marking number 2 All USARTdriver functions are listed which are automatically generated by Atmel | START Inspect thefunctions and pay attention to the functionality of USART_0_putc(const uint8_t data) andUSART_0_tx_empty() which have been used in this project Selecting a function will jump to thedeclaration of that functionFigure 3-5 USART Driver Function List



3 In the mainc file manually implement the function which will write a string to the USART TX bufferndash Declare a char array hello that holds Hello Worldn and a HELLO_LEN definition that

defines the string lengthconst char hello[]=Hello Worldndefine HELLO_LEN 13

ndash Implement a usart_put_string() function based on the USART_0_putc() andUSART_0_tx_empty() functions which are included in the usartc fileUSART Functionsvoid usart_put_string(const char str[] const uint8_t STR_LEN) for (int i=0 iltSTR_LEN i++) while(USART_0_tx_empty()) USART_0_putc(str[i])

ndash Add a call to usart_put_string() in the main() function before the while(1) loopusart_put_string(hello HELLO_LEN)

ndash The complete code for mainc looks as Figure 3-6 (the code in red markings are supposed tobe added in)Figure 3-6 Add USART Function in mainc

4 Build the solution by pressing F7 or clicking Build rarr Build Solution



Info The solution should build without errors

Result An application that transmits the string Hello World to USART have beenimplemented

33 USART Output to Data Visualizer Terminal

To do Set up the Data Visualizer terminal in Studio to display the string transmitted from theevaluation kit via the EDBG Virtual COM Port

1 In Studio 7 click Tools rarr Data Visualizer to open the Data Visualizer2 In the Data Visualizer window click Configuration located all the way to the left expand the

External Connection group and double-click Serial Port as illustrated by the steps in the figurebelow

3 Expand the drop-down list of COM ports in the Serial Port Control Panel and select the COM portassociated with the Virtual COM Port of the EDGB on the evaluation kit as shown in the figurebelow

Tip The EDBG Virtual COM Port number associated with the ATtiny Xplained Pro kitcan be found in Windows Device Manager by clicking Start rarr Control Panel rarr DeviceManager rarr Ports

4 Leave the serial port settings at default values and click Connect as shown in the figure below toopen the terminalFigure 3-7 Select USART Serial Port

5 Program the device and run the program by pressing Ctrl+Alt+F5 or by clicking Debug rarr StartWithout Debugging

6 Inspect the terminal in the Data Visualizer tab and verify that Hello World is printed as shown inthe figure below



Figure 3-8 String Printed to Terminal

Result Transmission of Hello World using USART has been verified with the Data Visualizerterminal

34 RTC Interrupt Triggers USART Transmission

To do Update the application to enable the RTC overflow interrupt to trigger the USARTtransmission of Hello World to the Data Visualizer Terminal

To do Add in the new mainh file

1 Right-click on the project ATtiny817_getting_start_events in Solution Explorer and click Add rarr NewItem as shown below



Figure 3-9 Add New Item

2 In the pop-up window choose Include File rename the file to mainh and click Add as shownbelow

Result An empty file named mainh will be added to the project and listed just below themainc file in Solution Explorer

Figure 3-10 Add mainh File

3 Locate the mainh file in Solution Explorer and open it

To do Update the newly created mainh file



4 Add the line extern volatile uint8_t sendflag in mainh as shown belowFigure 3-11 Updating mainh File

Info The variable sendflag will be used by the application in driver_isrc to initiateUSART transmissions

5 Open the driver_isrc file from Solution Explorer

To do Update the driver_isrc file

6 Make the sendflag variable available in the driver_isrc by including it as shown below7 Raise the flag by writing 1 to the sendflag variable in the RTC ISR as shown below This can

serve as a notification to the CPU that the RTC overflow interrupt has been executedFigure 3-12 Updating driver_isrc File

To do Update the mainc file



8 In mainc include the mainh file and declare the sendflag variable asinclude mainhvolatile uint8_t sendflag = 0

9 In mainc add the following code in the while(1) loop of the main() functionif (sendflag) usart_put_string(hello HELLO_LEN) sendflag = 0

This piece of code will check if sendflag is set and then call usart_put_string() to print theHello World string to the USART terminal The sendflag is set each time the RTC overflowinterrupt routine defined in driver_isrc is executed After the USART transmission sendflag is resetand ready for a new check

The complete modifications in the mainc file are highlighted in the red markings as shown below

Figure 3-13 Updating mainc File

10 Press F7 to build the solution




11 Program the kit and start the application by pressing Ctrl+Alt+F5 or by clicking Debug rarr StartWithout Debugging

Info The application should start executing on the kit

12 Open the Data Visualizer terminal and verify that Hello World is printed approximately two timesper second as shown belowFigure 3-14 RTC Interrupt Continuously Triggers String Print to Terminal

Result The RTC overflow interrupt continuously triggers USART transmission of the HelloWorld string to the Data Visualizer terminal two times per second



4 Assignment 3 ADC ISRRDY Interrupt Triggers ADC Data Output toUSART TerminalThe ATtiny817 has an ADC module which will be configured The application code will also be updatedA potentiometer will be connected to the ADC input pin to observe the added ADC functionality ADC datawill be sent to USART and observed in the Data Visualizer terminal window

This is based on the project Assignment 2 RTC Triggers Print to USART Terminal Here anapplication will be developed demonstrating the ADC functionality with ADC data output to the USARTterminal First use Atmel | START to add in the ADC drivers and then get the module configured Now twoADC functions must manually be added to Atmel Studio The RTC overflow interrupt will trigger the startof an ADC conversion and the ADC data ready interrupt will trigger sending the ADC data to the USARTterminal

Peripherals used

bull ADCbull USART (from previous assignment)bull RTC (from previous assignment)bull GPIO (PB4 from previous assignment)

Clock details

bull 3333 MHz ADC clockbull 3333 MHz main clock (from previous assignment)bull 1 kHz RTC clock (from previous assignment)

41 Add ADC Driver In Atmel | START

To do Add ADC driver to the project using Atmel | START

1 Open the ATtiny817_getting_started_events project from Assignment 22 Select the project name right-click in the Solution Explorer window and select Re-Configure Atmel

START Project

Info Atmel | START will be opened in the default web browser

3 Click in the Atmel | START window and expand Drivers from the ADDSOFTWARE COMPONENT window

4 Add the ADC to the project by selecting ADC and clicking



Result ADC driver is added to ATtiny817_getting_started_events

42 Configure ADC in Atmel | STARTOnce the ADC module has been added to ATtiny817_getting_started_events the ADC driver will beconfigured here

To do Configure the ADC Module

1 Click ADC_0 in the Atmel | START window2 Perform the configuration steps marked with red as depicted in Figure 4-1

ndash Enable the ADC by checking the ENABLE ADC Enable checkboxndash Enable PA6 as an analog input for the ADC by checking the PA6 checkbox Then select ADC

input pin 6 from the MUXPOSAnalog Channel Selection Bits dropdown menu to actuallyselect the enabled PA6 as ADC input pin

ndash Configure the ADC resolution to be 8-bit by selecting 8-bit mode from the RESSELADCResolution dropdown menu

ndash Configure the voltage reference REFSEL to be VDD from the dropdown menundash Enable the Result Ready interrupt by checking the RESRDYResult Ready Interrupt Enable

checkbox



Figure 4-1 ADC Configuration in Atmel | START



Note Clicking the question mark next to each configuration will provide the data sheet descriptionof the individual bit setting

3 Generate the project by clicking The following project summary windowpops upFigure 4-2 Summary of Project Code Generated by Atmel | START

4 Click View Diff on the driver_isrc file as in red marking in the Figure 4-2 A window pops upshowing the code difference between Assignment 2 version and the Atmel | START regeneratedversion asFigure 4-3 driver_isrc View Difference After Atmel START Modification



As shown the ISR(ADC0_RESRDY_vect) function has been added in while the two linesLED0_toggle_level() and sendflag = 1 are missing in the Atmel | START generated version ofcode The regenerated version needs to be updated including the code that existed in theAssignment 2 versionBy clicking on View Diff on other three files one can see that these files can simply be overwrittenwithout modification required

5 Now choose to regenerate the project in Atmel | START by selecting the three files as circled in redmarking in Figure 4-2 These three selected files do not require modification and will be overwrittenby the Atmel | START generated version of codes when clicking the OK button at the bottom in Figure 4-3 The mainc and driver_isrc files needs to be updated manually as driver_isrc is shownin Figure 4-3

Result The Atmel | START project has been regenerated in Atmel Studio including thenewly added ADC drivers

43 Add ADC Functionality to Application CodeOnce the ADC module has been added and reconfigured using Atmel | START the application codeneeds to be updated using Atmel Studio

To do Update the code in ATtiny817_getting_started_events to make use of the ADC driverjust added through Atmel | START Specifically update the mainc mainh and driver_isrc files

1 Update the code in mainc by performing the steps below The complete code after updating isshown in Figure 4-4

ndash Add a variable declaration for the ADC result adc_resultvolatile uint8_t adc_result = 0

ndash Add the function for starting an ADC conversion ADC_start_conversion() and thefunction for reading out the ADC result ADC_get_result()ADC Functionsvoid ADC_start_conversion() ADC0COMMAND = ADC_STCONV_bm Set start conversion enable mask bitvoid ADC_get_result() adc_result = ADC0RESL

ndash In the while-loop of the main function comment out the code which sent the hello stringfrom assignment 2 and add code for sending adc_result via the USART insteadusart_put_string(hello HELLO_LEN)USART_0_putc(adc_result)



Figure 4-4 Updates to mainc in Atmel Studio

2 Add a global declaration of the adc_result variable two functions ADC_start_conversion()and ADC_get_result() in mainh as shown in Figure 4-5Figure 4-5 Updates to mainh in Atmel Studio

3 Update the code in driver_isrc by following the steps shown in Figure 4-6ndash Add in include mainh in the headerndash Make the application code trigger an ADC conversion each time the RTC overflows by adding

ADC_start_conversion() to the RTC interrupt handler ISR(RTC_CNT_vect)ADC_start_conversion()



ndash Make the application code trigger a read-out of the ADC result for each ADC conversion byadding ADC_get_result() to the ADC interrupt handler ISR(ADC0_RESRDY_vect)ADC_get_result()

ndash Ensure that the new ADC result is sent to the terminal window using the USART by movingsendflag from the RTC interrupt handler to the ADC interrupt handlersendflag = 1

Figure 4-6 Updates to driver_isrc in Atmel Studio

4 Build the project by clicking or F7 Make sure there are no compiler errors or warnings

Result The ADC functionality code is done

44 Connect Potentiometer to ADCA potentiometer also called a potmeter is a three-terminal resistor with a sliding or rotating contact thatprovides an adjustable voltage divider As shown in the upper left corner of the figure below the potmeterhas three pins marked in red as 1 2 and 3 respectively

To do Connect a potentiometer to ATtiny817 Xplained Pro by using a breadboard and threemale-to-female cables

1 Place the potmeter in the breadboard and notice how the pins corresponds with the lettersnumberson the breadboard

2 Connect the pins of the potmeter to ATtiny817 Xplained Pro by using male-to-female cablesndash Pin 1 to VCCndash Pin 2 to PA6



ndash Pin 3 to GND

Figure 4-7 Potentiometer Connected to ATtiny817 Xplained Pro

45 Observe ADC FunctionalityNow the ADC driver has been added to the project the application code has been updated to make useof the ADC and the potentiometer has been connected to the ADC input pin It is time to observe theADC functionality using the Data Visualizer in Atmel Studio

Observe ADC functionality using Data Visualizer

1 Program the code by selecting Debug rarr Start Without Debugging or clicking on the top ofmenu bar

2 Open the Data Visualizer by clicking the Data Visualizer tab The output to the USART terminalshould look as shown in Figure 4-8Figure 4-8 Output from USART Terminal Window

Note The output in the USART terminal window is currently in ASCII format which does not givethe best readability when it comes to observing how turning the potmeter knob affects the output

3 Select the output format to be in hexadecimal values by checking the Hexadecimal Values check-box as depicted in red marking in Figure 4-9



Figure 4-9 Output in Hex Format from USART Terminal Window

Result By rotating the potentiometer knob the voltage input to ADC input pin PA6 ischanging This can be observed as the ADC result being sent to USART terminal window ischanging as one rotates the knob

Note When rotating the potentiometer knob the ADC result printed in the USART terminal window is inthe range of 0x00-0xFF This is expected as the ADC resolution has been configured to be 8 bits



5 Assignment 4 ADC WCMP Interrupt Triggers ADC Data Print to DataVisualizerIn this assignment an application will be developed that will configure ADC Window Comparison (WCMP)interrupt triggering ADC data print to USART terminal and graph in Data Visualizer

The ADC window comparison is a feature which allows the user to further filter the ADC output in theirpredefined way It is enabled when the window comparator interrupt enable (INTCTRLWCOMP) bit isset There are four window mode options output ADC results only when they are below window abovewindow within window or outside window The mode is configured by writing the CTRLEWINCM fieldWINLT andor WINHT registers also need to be configured to set the window comparator to low andorhigh threshold The ADC interrupt will then be triggered when the ADC output is available and it alsosatisfies the configured mode

First Atmel | START will be used within Atmel Studio to reconfigure the project from Assignment 3 InAtmel | START the ADC driver will be updated using the WCMP interrupt option instead of a result ready(RESRDY) interrupt

51 ADC Re-Configuration in Atmel START1 Open the ATtiny817_getting_started_events project from Assignment 32 Right-click on the project name ATtiny817_getting_started_events in Solution Explorer and then

right-click Re-Configure Atmel Start Project3 In the Atmel | START window click the ADC component4 Scroll down and reconfigure ADC as shown in Figure 5-1 Reconfiguration is shown with red

markingsFigure 5-1 ADC Reconfiguration in START

5 Take a look at the configuration steps described belowndash Unselect the checkbox for the RESRDY Result Ready Interrupt Enable fieldndash Select the checkbox for the WCMP Window Comparator Interrupt Enable field as it now

replaces the just unselected RESRDY interruptndash Select Outside Window from the WINCM Window Comparator Mode dropdown menundash Enter 200 (0xc8 hexadecimal value) in the WINHT Window Comparator High Threshold field



ndash Enter 100 (0x64 hexadecimal value) in the WINLT Window Comparator Low Threshold field6 Click the GENERATE PROJECT button at the bottom of the window in order to regenerate the

project in Atmel Studio The project summary window pops up as shown in Figure 5-2Figure 5-2 Project Code Regenerated

7 For the driver_isrc file click on View Diff in red marking to see the difference before and after theAtmel | START regeneration as shown belowFigure 5-3 Driver_isrc View Diff

8 mainc and driver_isrc are not checked as in Figure 5-2 and need to be manually modifiedafterward



Click OK to regenerate the project

Result The Atmel | START project has been regenerated in Atmel Studio including thenewly updated ADC drivers

52 Update Application in Atmel Studio and Output ADC Data to Data VisualizerGraph

To do Update the code in the driver_isrc file

1 In Atmel Studio open the driver_isrc file and replace the ISR(ADC0_RESRDY_vect) function withthe ISR(ADC0_WCOMP_vect) function as shown below in red markingFigure 5-4 Driver_isrc Updates

2 Click the Data Visualizer tab and expand the Configuration tab on the left side of the window ClickVisualization and double-click Graph as shown below



Figure 5-5 Data Visualizer Graph Selection

3 As shown in Figure 5-6 (red marking number 1) drag the terminal input from Serial Port ControlPanel to the New plot in the Graph window to connect the terminal input to the graph Then selectinput as Points (red marking number 2)



Figure 5-6 Data Visualizer Graph Data Output

4 Program the code by selecting Debug rarr Start Without Debugging5 Rotate the potmeter and observe the plotted ADC data in the Graph6 Observe that the plotted points for the ADC value matches the ADC value printed in the Terminal

(red marking number 3 in Figure 5-6) When the ADC value is within the 100-200 range points arenot plotted in the Graph Observe that the plotted values in the graph in the Figure 5-6 matches theADC values printed in the terminal outlined by red marking number 3

Result The Data Visualizer Graph shows the plotted ADC data



6 Assignment 5 RTC Interrupt Replaced by Event SystemIn this assignment the RTC overflow event signal instead of the RTC overflow interrupt will be used totrigger an ADC conversion

The Event System (EVSYS) enables direct peripheral-to-peripheral signaling It allows a change in oneperipheral (the Event Generator) to trigger actions in the other peripherals (the Event Users) throughEvent channels without using the CPU A channel path can either be asynchronous or synchronous to themain clock

Here the RTC overflow event signal will be used to trigger an ADC conversion

61 Event System Configuration in Atmel START

To do Configure Event system in Atmel | START

1 Open project ATtiny817_getting_started_events assignment 42 Right-click on ATtiny817_getting_started_events in the Solution Explore window and select Re-

Configure Atmel Start Project3 In the Atmel | START window click the ADD SOFTWARE COMPONENT box and then expand

Drivers from the ADD SOFTWARE COMPONENT window4 Search for the Events driver select it and then click the Add Component(s) (Refer to Figure 2-4 for

adding component of RTC as an example)Note The Events driver will be added to the project Now the EVENT_SYSTEM peripheralconfiguration needs to be done

5 Configure Asynchronous Event Channel 0 as shown below (see the red markings numbered 1 to3)



Figure 6-1 Event Source Selection

Execute the configuration steps described below

ndash Select the EVENTS icon on the left side of the window (red marking number 1)ndash Select Asynchronous Event Channel 0 (red marking number 2) and the EVENT SYSYEM

SETTINGS window pops upndash In the popped up EVENT SYSTEM SETTINGS window scroll down and select the Real Time

Counter overflow option and close the window6 Now configure the Event user as shown in Figure 6-2 below (see the red markings numbered 1 to

3)ndash Click the settings dialog under USERS rarr ADC0 (red marking number 1)ndash In the popped up EVENT SYSTEM SETTINGS window select the checkbox of Start Event

Input Enable (red marking number 2)ndash Select Asynchronous Event Channel 0 (red marking number 3) as ASYNCUSER1 and close

the window

Figure 6-2 Event Channel Selection



Info The Event system configuration is now completed with the event generator eventchannel and event user defined as shown below

Figure 6-3 Event User Selection

7 RTC will be reconfigured in Atmel | STARTClick DASHBOARD on the left side of the window and click on the existing RTC_0 module toreopen the RTC configuration window Unselect the checkbox for OVF Overflow Interrupt enable inthe red marking as shown below

Figure 6-4 RTC Reconfiguration

8 Click the GENERATE PROJECT button The project summary window pops up as shown in thefigure blow



Figure 6-5 Project Summary After Regenerated

9 Click View Diff for the srcadc_windowc file (see the red marking) to inspect the difference asshown belowFigure 6-6 driver_isrc View Diff

10 Tick the checkbox in order to overwrite the srcadc_windowc file11 Click OK to regenerate the project with overwriting adc_window

62 Event System Driver Code Development

To do Add code in driver_isrc to send ADC data to the terminal when the result is outside ofthe configured window range

1 Update the driver_isrc file



ndash Add include ldquomainhrdquo as the difference is shown in Figure 6-6ndash Add in the two lines of ADC_get_result() and sendflag=1 in the

ISR(ADC0_WCOMP_vect) function as shown in the comparison figure abovendash The ISR(RTC_CNT_vect)() function should now have been removed as it has been

replaced by event system2 The complete code of the driver_isrc looks like

include ltdriver_inithgtinclude ltcompilerhgtinclude mainh

ISR(ADC0_WCOMP_vect) Insert your ADC window comparator interrupt handling code here ADC_get_result() sendflag = 1 The interrupt flag has to be cleared manually ADC0INTFLAGS = ADC_WCMP_bm



4 Run the project by clicking Starting Without Debugging or use the hot-key CTRL+ALT+F5


5 Click the Data Visualizer tab Now the potentiometer can be adjusted The ADC data printed in theterminal and the plotted ADC data shown in the graph should have the same behavior as shown in Figure 5-6

Result The Event system functions as expected and has successfully replaced the RTCoverflow interrupt



7 ConclusionThis training demonstrated configuring RTC triggering ADC conversation using interrupt or event systemWith the feature of Atmel Studio 7 Data Visualizer it is easy to check the data output on the USARTterminal or even in the graph view

With Atmel | START it is easy to configurereconfigure a project by addingremoving peripheral driversand use automatically generated driver functions in the code

With Atmel Studio it is easy to run real-time debugging of an application and use IO view whichprovides register view capability and allows modifying the microcontroller registers in real-time It ispossible to debug the application using various debugging methods such as

bull Breakpointsbull IO view



8 Revision HistoryDoc Rev Date Comments

A 082017 Initial document release



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To register access the Microchip web site at httpwwwmicrochipcom Under ldquoSupportrdquo click onldquoCustomer Change Notificationrdquo and follow the registration instructions

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Users of Microchip products can receive assistance through several channels

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Customers should contact their distributor representative or Field Application Engineer (FAE) for supportLocal sales offices are also available to help customers A listing of sales offices and locations is includedin the back of this document

Technical support is available through the web site at httpwwwmicrochipcomsupport

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Note the following details of the code protection feature on Microchip devices

bull Microchip products meet the specification contained in their particular Microchip Data Sheetbull Microchip believes that its family of products is one of the most secure families of its kind on the

market today when used in the intended manner and under normal conditionsbull There are dishonest and possibly illegal methods used to breach the code protection feature All of

these methods to our knowledge require using the Microchip products in a manner outside theoperating specifications contained in Microchiprsquos Data Sheets Most likely the person doing so isengaged in theft of intellectual property

bull Microchip is willing to work with the customer who is concerned about the integrity of their code



bull Neither Microchip nor any other semiconductor manufacturer can guarantee the security of theircode Code protection does not mean that we are guaranteeing the product as ldquounbreakablerdquo

Code protection is constantly evolving We at Microchip are committed to continuously improving thecode protection features of our products Attempts to break Microchiprsquos code protection feature may be aviolation of the Digital Millennium Copyright Act If such acts allow unauthorized access to your softwareor other copyrighted work you may have a right to sue for relief under that Act

Legal NoticeInformation contained in this publication regarding device applications and the like is provided only foryour convenience and may be superseded by updates It is your responsibility to ensure that yourapplication meets with your specifications MICROCHIP MAKES NO REPRESENTATIONS ORWARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED WRITTEN OR ORAL STATUTORYOR OTHERWISE RELATED TO THE INFORMATION INCLUDING BUT NOT LIMITED TO ITSCONDITION QUALITY PERFORMANCE MERCHANTABILITY OR FITNESS FOR PURPOSEMicrochip disclaims all liability arising from this information and its use Use of Microchip devices in lifesupport andor safety applications is entirely at the buyerrsquos risk and the buyer agrees to defendindemnify and hold harmless Microchip from any and all damages claims suits or expenses resultingfrom such use No licenses are conveyed implicitly or otherwise under any Microchip intellectualproperty rights unless otherwise stated

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GestIC is a registered trademark of Microchip Technology Germany II GmbH amp Co KG a subsidiary ofMicrochip Technology Inc in other countries

All other trademarks mentioned herein are property of their respective companiescopy 2017 Microchip Technology Incorporated Printed in the USA All Rights Reserved



ISBN 978-1-5224-2066-8

Quality Management System Certified by DNV

ISOTS 16949Microchip received ISOTS-169492009 certification for its worldwide headquarters design and waferfabrication facilities in Chandler and Tempe Arizona Gresham Oregon and design centers in Californiaand India The Companyrsquos quality system processes and procedures are for its PICreg MCUs and dsPICreg

DSCs KEELOQreg code hopping devices Serial EEPROMs microperipherals nonvolatile memory andanalog products In addition Microchiprsquos quality system for the design and manufacture of developmentsystems is ISO 90012000 certified



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Worldwide Sales and Service


Prerequisites

Introduction

Table of Contents

1 Icon Key Identifiers

2 Assignment 1 RTC Overflow Interrupt Triggers LED Toggling

21 Atmel | START Project Creation

22 Atmel | START Project Overview In Atmel Studio

23 Code Development


3 Assignment 2 RTC Interrupt Triggers String Sent to USART Terminal





4 Assignment 3 ADC ISRRDY Interrupt Triggers ADC Data Output to USART Terminal


42 Configure ADC in Atmel | START

43 Add ADC Functionality to Application Code

44 Connect Potentiometer to ADC

45 Observe ADC Functionality

5 Assignment 4 ADC WCMP Interrupt Triggers ADC Data Print to Data Visualizer

51 ADC Re-Configuration in Atmel START

52 Update Application in Atmel Studio and Output ADC Data to Data Visualizer Graph

6 Assignment 5 RTC Interrupt Replaced by Event System



7 Conclusion

8 Revision History



Customer Support


Legal Notice

Trademarks



The peripherals used to create applications are GPIO RTC ADC CPUINT USART and Event System

Figure 1 ATtiny817 Xplained Pro

The following topics are covered

bull Driver configuration in Atmel STARTbull PINMUX driver configurationbull LED toggling triggered by RTC overflow interruptbull USART configuration with string print to USART serial-port terminalbull RTC overflow interrupt triggers an ADC conversion and then ADC result-ready interrupt triggers ADC

data print to USART terminalbull RTC overflow interrupt triggers an ADC conversion and then an ADC result triggers ADC data print to

USART terminal if it is outside a defined windowbull RTC overflow event triggers an ADC conversion then if an ADC result is outside a defined window

waking up CPU with an IRQbull How to use Data Visualizer in Atmel Studio to view the USART print to the embedded terminal and

graph



Table of Contents

Prerequisites1

Introduction1







7 Conclusion51




Customer Support 53


Legal Notice54


Trademarks 54


















Peripherals used


Clock details


































prescaler to 32















































































Figure 2-13 IO View




clicking






Peripherals used


Clock details










































































































Peripherals used


Clock details





START Project














checkbox







































ndash Pin 3 to GND




































































the window


















































Customer Support

























ISBN 978-1-5224-2066-8












Prerequisites

Introduction

Table of Contents





23 Code Development



















7 Conclusion

8 Revision History



Customer Support


Legal Notice

Trademarks



Table of Contents

Prerequisites1

Introduction1







7 Conclusion51




Customer Support 53


Legal Notice54


Trademarks 54


















Peripherals used


Clock details


































prescaler to 32















































































Figure 2-13 IO View




clicking






Peripherals used


Clock details










































































































Peripherals used


Clock details





START Project














checkbox







































ndash Pin 3 to GND




































































the window


















































Customer Support

























ISBN 978-1-5224-2066-8












Prerequisites

Introduction

Table of Contents





23 Code Development



















7 Conclusion

8 Revision History



Customer Support


Legal Notice

Trademarks



Trademarks 54


















Peripherals used


Clock details


































prescaler to 32















































































Figure 2-13 IO View




clicking






Peripherals used


Clock details










































































































Peripherals used


Clock details





START Project














checkbox







































ndash Pin 3 to GND




































































the window


















































Customer Support

























ISBN 978-1-5224-2066-8












Prerequisites

Introduction

Table of Contents





23 Code Development



















7 Conclusion

8 Revision History



Customer Support


Legal Notice

Trademarks
















Peripherals used


Clock details


































prescaler to 32















































































Figure 2-13 IO View




clicking






Peripherals used


Clock details










































































































Peripherals used


Clock details





START Project














checkbox







































ndash Pin 3 to GND




































































the window


















































Customer Support

























ISBN 978-1-5224-2066-8












Prerequisites

Introduction

Table of Contents





23 Code Development



















7 Conclusion

8 Revision History



Customer Support


Legal Notice

Trademarks





























prescaler to 32















































































Figure 2-13 IO View




clicking






Peripherals used


Clock details










































































































Peripherals used


Clock details





START Project














checkbox







































ndash Pin 3 to GND




































































the window


















































Customer Support

























ISBN 978-1-5224-2066-8












Prerequisites

Introduction

Table of Contents





23 Code Development



















7 Conclusion

8 Revision History



Customer Support


Legal Notice

Trademarks














































































Figure 2-13 IO View




clicking






Peripherals used


Clock details










































































































Peripherals used


Clock details





START Project














checkbox







































ndash Pin 3 to GND




































































the window


















































Customer Support

























ISBN 978-1-5224-2066-8












Prerequisites

Introduction

Table of Contents





23 Code Development



















7 Conclusion

8 Revision History



Customer Support


Legal Notice

Trademarks





Peripherals used


Clock details










































































































Peripherals used


Clock details





START Project














checkbox







































ndash Pin 3 to GND




































































the window


















































Customer Support

























ISBN 978-1-5224-2066-8












Prerequisites

Introduction

Table of Contents





23 Code Development



















7 Conclusion

8 Revision History



Customer Support


Legal Notice

Trademarks



































































































Peripherals used


Clock details





START Project














checkbox







































ndash Pin 3 to GND




































































the window


















































Customer Support

























ISBN 978-1-5224-2066-8












Prerequisites

Introduction

Table of Contents





23 Code Development



















7 Conclusion

8 Revision History



Customer Support


Legal Notice

Trademarks











checkbox







































ndash Pin 3 to GND




































































the window


















































Customer Support

























ISBN 978-1-5224-2066-8












Prerequisites

Introduction

Table of Contents





23 Code Development



















7 Conclusion

8 Revision History



Customer Support


Legal Notice

Trademarks







































ndash Pin 3 to GND




































































the window


















































Customer Support

























ISBN 978-1-5224-2066-8












Prerequisites

Introduction

Table of Contents





23 Code Development



















7 Conclusion

8 Revision History



Customer Support


Legal Notice

Trademarks





























































the window


















































Customer Support

























ISBN 978-1-5224-2066-8












Prerequisites

Introduction

Table of Contents





23 Code Development



















7 Conclusion

8 Revision History



Customer Support


Legal Notice

Trademarks

















































Customer Support

























ISBN 978-1-5224-2066-8












Prerequisites

Introduction

Table of Contents





23 Code Development



















7 Conclusion

8 Revision History



Customer Support


Legal Notice

Trademarks















ISBN 978-1-5224-2066-8












Prerequisites

Introduction

Table of Contents





23 Code Development



















7 Conclusion

8 Revision History



Customer Support


Legal Notice

Trademarks









Prerequisites

Introduction

Table of Contents





23 Code Development



















7 Conclusion

8 Revision History



Customer Support


Legal Notice

Trademarks



avrapps-1544: getting started with events on the tinyavr 1...

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